In applications requiring heavy bolted sections, or in bus-bar applications, washers having a spring characteristic are known and have been used. One type in the art, long well-known and used, is a “Belleville spring” washer. However, due to thermal expansion of bolts in various engineering applications, a looseness is generated in the bolted sections. Statistics, in terms of a bolt clamping force vs. a tightening torque for bolts, have been generated to assist in knowing just what “Belleville spring” washer is best for the load (and its nature, such as electrical, for example) under consideration. While prior art consists of conical spring washers and washers with a relief to provide a tighter fastening, looseness has been found to creep into the bolted section when not desired.
Specifically, the prior art in U.S. Pat. No. 5,829,933 ('933) achieves a tight fastening through the combination of the serrations and a relief provided in the washer's top surface. The relief, however, does not permit sufficient flexing of the washer, and looseness still may be generated in the bolted sections. Besides the looseness, an additional disadvantage in the '933 patent is the lack of maintaining an optimal electrical connection if piercing or biting into insulation is required.
Similarly, prior art French Standard No. E 25-511 discloses a conical spring washer to provide a tighter fastening through serrations and the presence of an annular relief. The annular relief, however, similar to the '933 patent, does not permit for sufficient flexing of the washer, does not provide for a tight non-loosening connection of a bolt or nut to a bearing surface, and lacks the capability to allow for an optimal electrical connection.
Additional prior art consists of a plurality of projections provided on the bottom surface of a washer to prevent the washer from slipping on a contacting surface. The point of each of those projections is to bite into the bearing surface to maintain a tighter fastening of a bolt or nut to the bearing surface. The disadvantage, however, is that this allows for frictional damage or heating to occur on the contacting surface because of an uneven frictional coefficient between the washer and bearing surface.
In view of such difficulties, there is a need for a washer to provide a tighter fastening of a bolt or nut to the bearing surface in order to prevent a loosening connection, as well as to provide a better electrical connection.